The present invention concerns new photochromic compounds of the indolino-spiro-oxazine type, a method for their preparation, as well as compositions and articles with photochromic properties containing at least one of said photochromic coumpounds. Generally speaking the compounds of the present invention can be used advantageously in making all sorts of optical lenses, the term optical lens mainly referring to an ophthalmic lens, a contact lens, or a sun protection lens.
Photochromism is a well known reversible phenomenom which is illustrated typically by a compound which undergoes a change in color when exposed to light radiations, including those in the U. V. range, such as sunlight, and returns to its original color upon stopping light exposure.
Such compounds are useful for example in the manufacture of lenses for sunlight-protection glasses or in other applications involving the need for making the transparency of an article vary according to ambient light intensity. They can be applied onto a transparent support or incorporated within a transparent polymerized organic material, in combination with a large variety of polymer compositions.
A number of organic photochromic compounds having a formula including an indolino-spiro-oxazine group have already been provided for such uses, especially in the field of sunlight protection lenses.
U.S. Pat. Nos. 3,562,172 and 3,578,602 have thus disclosed compounds showing a photochromic effect which belong to the family of indolino-spiro-naphthoxazines, while U.S. Pat. No. 4,215,010 describes indolino-spironaphtoxazines wherein the naphthalene nucleus comprises methoxy, ethoxy or halogen substituents. Similar photochromic compounds comprising a pyridobenzene nucleus instead of the naphthalene nucleus in the compounds above are described in U.S. Pat. No. 4,720,547, as well as in the international patent application WO 87/00524.
Nevertheless, the compounds described in that prior art do not fully satisfy all the qualities that one expects from them. Considering more specifically the scope of their uses in lenses for sunlight protection, the photochromic material obtained, whether from a solution of the photochromic compound or by incorporating it into an organic polymer, should show a number of properties concerning the photochromic effect in addition to its natural transparency and its compatibility with the materials currently used for such lenses.
In particular:
When it is irradiated in the range of its photosensitivity, its coloration should appear rapidly, within a time preferably of the order of a second, and it should disappear when irradiation is stopped with similar rapidity.
The material should be stable in time, as well in itself as in its photochromism. Thus, the compound should be able within the material, to support a great number of coloration, decoloration sequences throughout a long period of use which may extend to several years.
The colorability should be good for reasonable contents of the photochromic compounds, and the absorption spectrum of the irradiated material should cover the whole of the visible spectrum as far as possible.
The photochromic effect should preferably be independent of the substrate containing the compound and it should occur at all temperatures within a large range, i.e. at variable ambient temperatures as well as when it is heated under irradiation.
The coloration showed by the material under radiation should also answer to aesthetic requirements and preserve a pleasant sight of the surroundings for those wearing glasses or ophthalmic lenses made of such materials. From that point of view one should avoid the blue colors which are generally encountered with the compounds of the prior art above and green should be preferred.